Abstract
Highway signs provide important information to drivers to assist in navigation, to identify potentially hazardous roadway locations, and to remind drivers of safe operating practices. Ensuring that signs have sufficient visibility to the driving public is a key undertaking by transportation agencies. In order to assist in evaluating and comparing different materials for photometric and visual performance, the present study was undertaken to assess the utility of specifying sign sheeting performance in terms of visual performance. As part of this effort, a practical methodology for conducting field measurements of sign luminance along roadways was developed. In addition to describing the methods for an approach to visual performance based specifications, a spreadsheet tool for calculating minimum sign luminance and visibility from different sign sheeting materials was also developed.
Highlights
Highway signs are critical elements of the roadway infrastructure, providing important information to drivers to assist in navigation, to identify potentially hazardous roadway locations, and to remind drivers of safe operating practices
The correlation between the measured values in each session, as well as the differences between sign material types that were consistent with the ASTM D4956-16 type specifications, suggests that it is possible to differentiate among different sign sheeting material types based on field luminance measurements
The lowest measured luminance value in the second measurement set could have been caused by extraneous light sources in the scene when the headlightsoff measurement was made, or by a slight misorientation of the measurement vehicle away from the signs for this particular measurement. Notwithstanding this single measurement, which corresponds to less than 3% of the total number of field measurements made in the present study, the measured data and corresponding Relative Visual Performance (RVP) analyses confirm that the measured signs meet or exceed the minimum performance requirements for both types of highly reflective sign sheeting materials used in the measurement location for the present study
Summary
Highway signs are critical elements of the roadway infrastructure, providing important information to drivers to assist in navigation, to identify potentially hazardous roadway locations, and to remind drivers of safe operating practices. RVP quantities tend to exhibit a plateau and escarpment quality whereby once light level, contrast and size provide a high level of visual performance, further increases in any of these factors will not substantially improve visual performance (it is said to be on the plateau). If light level, contrast or size were to decrease enough to place visual performance on the edge of the plateau, even small reductions in any of these factors could result in large decrements in visibility. Quantities derived from the RVP model were highly correlated with visual acquisition times for simulated overhead guide signs varying in luminance and contrast, measured by Schnell et al (2009). The RVP model is used in this study as a way to describe the visibility of sign symbols and characters based on their luminance, contrast, and size characteristics, for different geometric conditions and by drivers varying in age. It was necessary to conduct field measurements to identify the range of luminances of guide signs in an existing real-world sign installation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
